In general, an exhaust gas recirculation (EGR) device refers to a device for inhibiting the occurrence of nitrogen oxide (NOx) by recirculating a part of exhaust gas to an intake system to decrease a combustion temperature in a cylinder.
That is, the EGR device serves to recirculate a part of the exhaust gas discharged from an engine to an intake line, thereby reducing the amount of oxygen in a gaseous mixture, reducing the amount of discharged exhaust gas, and reducing hazardous substances in the exhaust gas.
The EGR device includes an EGR cooler that cools exhaust gas. The EGR cooler serves as a kind of heat exchanger that performs heat exchange between exhaust gas and a coolant, thereby preventing a temperature of the exhaust gas from being excessively increased.
Further, the EGR cooler includes a housing and multiple tubes stacked in the housing. In this case, coolant passageways are formed in the housing, and exhaust gas passageways are formed in the tubes. The multiple tubes are spaced apart from one another at predetermined intervals and stacked in the housing, and the multiple tubes are installed by being brazed to the housing.
However, the EGR cooler in the related art has a problem in that the tube sags downward due to its own weight when brazing the housing and the tube. In addition, the EGR cooler in the related art also has a problem in that the housing swells when testing the housing for a leakage of coolant.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.